The adsorption site of pyridine (C 5 H 5 N) on Ni(111) has been investigated by scanned-energy mode photoelectron diffraction using the N 1s core level. It was found that the nitrogen atom adsorbs close to the atop position with an angle of 18°(+ 2°/ -4°) between the N-Ni bond and the surface normal. The N-Ni bond length is 1.97 ±0.03 Since recent X-ray absorption studies show that the π system of the pyridine is also tilted by about 20° away from the surface normal, we conclude that the N-Ni bond and the ring plane are co-planar.